1. Field of the Invention
This invention relates to hybrid compositions comprising silicone-polyester-polysilicate and to the use of such compositions for coating substrates.
2. Description of the Prior Art
Silicone resin is a kind of resin with good properties of thermal and weather resistance, and has been broadly used as heat-resistant and weather-resistant protective coating. Due to the nature of silicone resin has a poor compatibility with general organic macromolecules, employing organic macromolecules to modify silicone resin can improve the compatibility of silicone resin and organic macromolecules. Silicone-polyester resin is one kind of those. Silicone-polyester resin can not only improve the compatibility of silicone and organic macromolecules but also increase the mechanical character of silicone such as the film hardness and brittleness. Silicone-polyester resin can be broadly used as the non-stick coating for cookware, for example, flat or frying pans and bakeware such as baking trays, as well as the metal weather-resistant and heat-resistant protective coating such as the coating of electric irons. Many commercial products of silicone-polyester resin are sold on markets, such as SILIKOFTAL® HTT sold by Degussa Tego Chemie Service GmbH, MIRASOL 13-A-8762 (trade mark) produced by CCP, and KR-5235® sold by Shin Etsu. The persistence of conventional silicone-polyester resin is not in an ideal status while the silicone-polyester resin is used as the majority of protective coating for thermal resistance to stand hot-oil at 260° C. The main reason is that the content of reactive function group is deficient. For example, the content of the functional group of Si—OH is about 2-7 wt. % while silicone resin contains it, or the content of the functional group of Si—OCH3 is about 15-22 wt. % while silicone resin contains it. The deficient content of the reactive function group makes the crosslinking density of synthesized silicone-polyester insufficient after curing. This leads the molecule structure of silicone-polyester to lack of denseness and the film in high temperature is easily penetrated by hot-oil. This further makes the film softened or blistered. The same reason, insufficient crosslinking density, also makes the hot hardness of the film in high temperature poor. Hence, increasing the crosslinking density of silicone-polyester is an effective method to strengthen the thermal resistance for silicone-polyester resin after curing. In U.S. Pat. No. 4,683,271 issued by Lin, et al., U.S. Pat. No. 4,608,421 issued by Lin, and U.S. Pat. No. 5,227,435 issued by Kang, et al., the methods for synthesizing and producing the silicon-polyester coating powder compositions are set forth. In U.S. Pat. No. 4,788,106 issued by Short, adding epoxy silane, aluminum acetylacetonate, and tetraalkyl titanate as catalysts into silicone-polyester resin can decrease the baking temperature of the silicone-polyester resin to 120° C. In U.S. Pat. No. 4,521,461 issued by McVie, et al., adding epoxy silane and titanium chelate into silicone-polyester resin can speed up the rate of cure of the silicone-polyester. In U.S. Pat. No. 4,472,465 issued by Burrill, adding amino silane and titanium chelate as catalysts into silicone-polyester resin can decrease the curing temperature of the silicone-polyester resin. In U.S. Pat. No. 4,465,712 issued by McVie, adding amino silane and a silane having 3 or 4 alkoxy or alkoxyalkoxy groups attached to silicone into silicone-polyester resin and baking them at 80° C. for two hours can increase the solvent resistance. However, the patents mentioned above are put in uses of metals or plastics protective coating and the main object is to decrease the curing temperature of silicone-polyester resin, but do not mention about the nature characters of compositions such as heat resistance. This invention differs to the patents mentioned above is that the main object of the present invention is to increase the crosslinking density of silicone-polyester resin and also to improve the thermal resistance such as hot-oil resistance and the hot hardness.